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Coordination of beam forming in wireless communication systems |
| 7197337 |
Coordination of beam forming in wireless communication systems
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| Patent Drawings: | |
| Inventor: |
Goldberg, et al. |
| Date Issued: |
March 27, 2007 |
| Application: |
10/730,671 |
| Filed: |
December 8, 2003 |
| Inventors: |
Goldberg; Steven Jeffrey (Downingtown, PA)
Chotkowski; Kimberly (West Chester, PA)
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| Assignee: |
InterDigital Technology Corporation (Wilmington, DE) |
| Primary Examiner: |
Mehrpour; Melody |
| Assistant Examiner: |
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| Attorney Or Agent: |
Volpe and Koenig, P.C. |
| U.S. Class: |
455/562.1; 342/368; 455/561 |
| Field Of Search: |
455/562.1; 455/561; 455/13.3; 455/63.4; 455/53.4; 342/368 |
| International Class: |
H04M 1/00; H01Q 3/00; H04B 1/38 |
| U.S Patent Documents: |
5258764; 6225961; 6417803; 6665545; 6768454; 6894643; 2001/0031647; 2003/0043435; 2004/0204108; 2005/0020311 |
| Foreign Patent Documents: |
1071228; 2581798; 200427345; 03/007420 |
| Other References: |
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| Abstract: |
A method and system for coordinating the use of beam forming between two communicating entities in a wireless communication system is disclosed. The two entities may communicate control information regarding their respective use of beam forming. A correction factor for at least one entity is provided wherein said entity may reduce or withhold its beam adjustment in order to correct any error measured in the alignment of its beam with respect to the beam of the other entity with which it is communicating. |
| Claim: |
What is claimed is:
1. A method for coordinating the use of beam forming between two communicating entities wherein control information regarding the use of beam forming is not communicatedbetween the two entities, the method comprising the steps of: selecting one of the two communicating entities for reduction of its beam adjustment; measuring an error in the alignment of beams emanating from the two communicating entities; determininga correction factor that is a fraction of said measured error; and adjusting the beam of the selected entity in an amount equal to the correction factor, whereby said adjusted beam is aligned with the beam transmitted by the unselected communicatingentity.
2. The method of claim 1 wherein the two communicating entities are a base station and a WTRU.
3. The method of claim 1 wherein the two communicating entities are two WTRUs.
4. The method of claim 1 further comprising the step of: repeating the measuring and adjusting steps until the error measured is below a predetermined value.
5. The method of claim 1 wherein the fraction is 0.5.
6. The method of claim 1 wherein the error measurement and beam adjustment is performed in the azimuth dimension.
7. The method of claim 1 wherein the error measurement and beam adjustment is performed in the elevation dimension.
8. The method of claim 1 wherein the error measurement and beam adjustment is performed in the azimuth and elevation dimensions.
9. A method for coordinating the use of beam forming between two communicating entities wherein control information regarding the use of beam forming is communicated between the two entities, the method comprising the steps of: measuring anerror in the alignment of beams emanating from the two communicating entities; determining a correction factor a fraction of said measured error for each of the entities wherein the sum of the two correction factors is equal to one; communicating thecorrection measurement between the entities; and adjusting the beam of both entities according to their respective correction factors, whereby the adjusted beam is aligned with the beam transmitted by the unselected communicating entity.
10. The method of claim 9 wherein the two communicating entities are a base station and a WTRU.
11. The method of claim 9 wherein the two communicating entities are two WTRUs.
12. The method of claim 9 wherein the error measurement and beam adjustment is performed in the azimuth dimension.
13. The method of claim 9 wherein the error measurement and beam adjustment is performed in the elevation dimension.
14. The method of claim 9 wherein the error measurement and beam adjustment is performed in the azimuth and elevation dimensions.
15. The method of claim 9 wherein the correction factor of one entity is zero thereby causing said entity to refrain from adjusting its beam.
16. A method for coordinating the use of beam forming between two communicating entities wherein control information regarding the use of beam forming is not communicated between the two entities, the method comprising the steps of: selectingone of the two communicating entities for reduction of its beam adjustment; measuring an error in the alignment of beams emanating from the two communicating entities; determining a correction factor that is a fraction of said measured error; and theunselected communicating entity refraining from adjusting its beam and the selected communicating entity adjusting its beam in accordance with said correction factor whereby the adjusted beam is aligned with the beam transmitted by the unselectedcommunicating entity.
17. A method for coordinating the use of beam forming between two communicating entities wherein control information regarding the use of beam forming is communicated between the two entities, the method comprising the steps of: measuring anerror in the alignment of beams emanating from the two communicating entities in the azimuth dimension; measuring an error in the alignment of beams emanating from the two communicating entities in the elevation dimension; determining a firstcorrection factor based on said measured error in the azimuth dimension for each of the entities for use in the azimuth dimension wherein the sum of the two first correction factors is equal to one; determining a second correction factor based on saidmeasured error in the elevation dimension for each of the entities for use in the elevation dimension wherein the sum of the two second correction factors is equal to one; adjusting the beam of both entities according to their respective firstcorrection factors wherein an error is detected in the azimuth dimension; and adjusting the beam of both entities according to their respective second correction factors wherein an error is detected in the elevation dimension.
18. A method for coordinating the use of beam forming between two communicating entities wherein control information regarding the use of beam forming is communicated between the two entities, the method comprising the steps of: selecting acorrection factor for each of the entities wherein the sum of the two correction factors is equal to one; each entity measuring an error in the alignment of beams emanating from the two communicating entities; and adjusting the beam of both entitiesaccording to their respective correction factors and error measurement, whereby the adjusted beams are aligned with beams emanating from the two communicating entities are aligned with respect to each other.
19. The method of claim 18 wherein the two communicating entities are a base station and a WTRU.
20. The method of claim 18 wherein the two communicating entities are two WTRUs.
21. The method of claim 18 wherein the error measurement and beam adjustment is performed in the azimuth dimension.
22. The method of claim 18 wherein the error measurement and beam adjustment is performed in the elevation dimension.
23. The method of claim 18 wherein the error measurement and beam adjustment is performed in the azimuth and elevation dimensions.
24. The method of claim 18 wherein the correction factor of one entity is zero thereby causing said entity to refrain from adjusting its beam.
25. A wireless communication system wherein beams may be adjusted to enhance wireless communications between wireless entities operating in the system, the wireless communication system comprising: a plurality of wireless entities, saidentities being capable of communicating using beam formed transmission and reception patterns and including a processor for measuring an error in the alignment of their own beam and the beam of another entity with which they are communicating; whereinat least one of two communicating wireless entities adjusts its beam a fraction of the error measured in the alignment of its beam with respect to the beam of the other wireless entity whereby the transmitted beams are aligned with each other.
26. The wireless communication system of claim 25 wherein the processor of the at least one communicating wireless entity is configured to adjust the beam of the at least one wireless entity in an amount equal to the fraction multiplied by theerror measured.
27. The wireless communication system of claim 26 wherein a first of the two communicating wireless entities includes a transmitter configured to transmit the fraction to a second of the two communicating wireless entities.
28. The wireless communication system of claim 27 wherein the second wireless entity includes a receiver configured to receive the fraction and further includes a processor to adjust the beam of the second wireless entity in an amount equal toone minus the fraction multiplied by the error measured.
29. The wireless communication system of claim 28 wherein the first wireless entity is a WTRU and the second wireless entity is a WTRU.
30. The wireless communication system of claim 28 wherein the first wireless entity is a WTRU and the second wireless entity is a base station.
31. A wireless transmit/receive unit (WTRU) configured to maintain alignment of its beam with the beam of another wireless entity with which the WTRU is communicating, the WTRU comprising: a first processor configured to measure an error in thealignment of a first beam emanating from the WTRU and a second beam emanating from the other wireless entity; and a second processor configured to compute a correction factor that is a fraction of said measured error and adjust the first beam in anamount equal to the correction factor multiplied by the error measured whereby the adjustment is less than or equal to 1 and said first beam is aligned with said second beam.
32. The WTRU of claim 31 further comprising: a transmitter configured to transmit the fraction of the measured error that the WTRU will adjust its beam to the wireless entity with which the WTRU is communicating.
33. The WTRU of claim 32 further comprising: a receiver configured to receive, from the wireless entity with which the WTRU is communicating, a second fraction with which the entity used to adjusts its beam; and wherein when a second fractionis received, the second processor being configured to compute the first fraction by subtracting one minus the second fraction and adjusting the first beam in an amount equal to the first fraction multiplied by the error measured.
34. The WTRU of claim 33 wherein the wireless entity with which the WTRU is communicating is another WTRU.
35. The WTRU of claim 33 wherein the wireless entity with which the WTRU is communicating is a base station. |
| Description: |
FIELD OF INVENTION
The present invention relates to wireless communication systems. More specifically, the present invention relates to coordination of beam forming in wireless communication systems.
BACKGROUND
Generally, beam forming is where transmission or reception of signal power is concentrated in the direction of an intended respective receiver or transmitter. Both the transmission and reception of signals can benefit from beam formed patternscompared to omni-directional patterns. From a transmitter's perspective, beam forming lessens the power needed to perform the transmission, and lessens the power causing interference directed to nonintentional receivers. From a receiver's perspective,beam forming enhances the desired received signal and lessens the interference due to other transmitters or signal sources the further they are removed from the primary axis of a transmission.
Referring to FIG. 1, beam forming is usually associated with fixed infrastructures such as microwave towers 10, 12, for example. This is because it is relatively easy to point static transmit and receive beams of microwave towers 10, 12 towardeach other as shown in FIG. 1. The structures on which the towers are mounted and the beam widths that are utilized simply need to be sufficiently stable so that the beams remain overlapped thereby providing reliable transmission. If towers or beamsare unstable due to structural or electrical instabilities, the beams may not adequately overlap as shown in FIG. 2. In such situations, however, correction is relatively easy because the beams are transmitted from two fixed locations and the degree ofmisalignment is typically relatively minor.
With rapidly increasing capacity and coverage requirements of wireless communication systems, however, beam forming may also be used between base stations and wireless transmit/receive units (WTRUs). Referring now to FIG. 3, there is shown abase station 20 that is using beam forming and a WTRU 22 that is using an omni-directional pattern. Ignoring possible external influences on the beam (i.e. physical obstructions), the base station 20 should have a reasonably static pattern position. The WTRU 22, on the other hand, is subject to rotation and location movement in any direction. If the transmission pattern of the WTRU 22 is truly omni-directional (i.e. approximated by a circle), rotation will have no effect on the communications link. Location movement, however, will pose a problem in that it can change the relationship of the WTRU 22 and base station 20 communication link. For example, in FIG. 3, WTRU 22 is initially emitting omni-directional pattern 24 and then changes location andbegins emitting omni-directional pattern 26. The base station 20 may therefore need to modify its beam to maintain contact. Extreme changes could of course require switching to another base station, which is called handoff (or handover) and occursnaturally in existing wireless communication systems.
Referring to FIG. 4, the base station 30 is using an omni-directional pattern and the WTRU 32 is using beam forming. Here, a further problem is introduced in that, because the WTRU 32 is using beam forming, location movement as well as rotationcan now deteriorate the pattern overlaps between the base station 30 and WTRU 32. For example, in this situation, WTRU 32 is initially emitting beam pattern 34 and then changes position as a result of rotation or location movement or both and beginsemitting beam pattern 36. This situation, however, can also be handled using handoff which, as mentioned, is an existing capability of existing systems. It should be noted that the omni-directional pattern of the base station 30 could be replaced by asectored pattern as is often found in wireless systems. The key point is that the base station 30 is providing complete coverage surrounding its location so that while rotation and location movement of a WTRU 32 may require handoff between sectors, thisis an existing capability of existing wireless systems.
As shown in FIG. 5, however, where both entities (i.e. a base station and WTRU) are using beam forming, movement by a WTRU 40 (see dashed patterns) is more likely to disrupt the pattern overlap. That is, while beam forming improvescommunications when properly aligned patterns are used, misalignment is more likely where both WTRUs and base stations use beam forming thereby making link establishment and maintenance more time consuming and difficult.
For example, in FIG. 6, the "before adjustment" situation shows two misaligned beams. In the prior art, the entities from which those beams originate Xa, Xb (both of which may be a base station or WTRU) both determine an adjustment to betteralign the beams, but since they are not aware of what the other is doing, they both perform the required adjustment. The net adjustment, therefore, causes a resultant error in alignment that is roughly equivalent to the original error, but with thebeams pointing in different directions as shown in the "post adjustment" situation. The next time the adjustments are attempted, the same thing can happen thereby causing the beams to fall into an oscillating pattern around the optimal alignment of thebeams. It is important to note that there is no implied timing relationship between the measurements or actual adjustments of the beams. Therefore, the only situation required to cause this problem is that the measurements made by one entity and theresultant adjustment that is performed are time overlapping with the same measurements and resultant adjustment occurring at another entity.
What is needed, therefore, is a method and system for coordination of beam forming in wireless communication systems.
SUMMARY
The present invention is a method and system for coordinating the use of beam forming between two communicating entities in a wireless communication system. The two entities may communicate control information regarding their respective use ofbeam forming. A correction factor for at least one entity is provided wherein said entity may reduce or withhold its beam adjustment in order to correct any error measured in the alignment of its beam with respect to the other entity with which it iscommunicating.
Another embodiment of the invention is applicable when one or both of the entities are unaware as to whether the other is capable of beamforming. A correction factor is therefore calculated and used by one entity in a fashion that will bepractical whether or not the other entity is capable of beamforming, or whether or not the other entity is utilizing the present invention.
BRIEF DESCRIPTION OF THE DRAWING(S)
FIG. 1 is a fixed transmitter and a fixed receiver having beamed formed transmissions that are properly aligned according to the prior art.
FIG. 2 is a fixed transmitter and a fixed receiver having beamed formed transmissions that have become misaligned according to the prior art.
FIG. 3 is a base station using beam forming and a WTRU using an omni-directional pattern according to the prior art.
FIG. 4 is a base station using an omni-directional pattern and a WTRU using beam forming according to the prior art.
FIG. 5 is a base station and a WTRU wherein their respective beams may become misaligned due to movement of the WTRU according to the prior art.
FIG. 6 is two entities Xa, Xb (both of which may be a base station or a WTRU) attempting to correct misalignment of their respective beams according to the prior art.
FIG. 7 is a table illustrating an example of transmission pattern scenarios where a base station and WTRU are capable of beam forming.
FIG. 8a is a base station and a WTRU correcting misalignment of their respective beams in an azimuth dimension according to a first embodiment of the invention.
FIG. 8b is a base station and a WTRU correcting misalignment of their respective beams in an elevation dimension according to a first embodiment of the invention.
FIG. 9a is a base station and a WTRU correcting misalignment of their respective beams in an azimuth dimension according to a second embodiment of the invention.
FIG. 9b is a base station and a WTRU correcting misalignment of their respective beams in an elevation dimension according to a second embodiment of the invention.
FIG. 10 is a wireless communication system wherein wireless entities operating within the system may adjust their beams to enhance communications within the system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Herein, a wireless transmit/receive unit (WTRU) includes but is not limited to a user equipment, mobile, mobile station, receiver, transmitter, fixed or mobile subscriber unit, pager, or any other type of device capable of operating in a wirelessenvironment. When referred to herein, a base station includes but is not limited to a Node-B, receiver, transmitter, site controller, access point or any other type of interfacing device in a wireless environment.
Further, it is important to note that like any antenna pattern, the outline of a beam shown in a drawing is merely a depiction of the signal attenuated a specified amount from the maximum energy within the pattern. The signal actually continuesbeyond the outline, but at an additionally attenuated level. The patterns shown in the figures herein are meant to depict levels at which communications are possible. These levels are in fact subject to both transmitter and receiver capabilities. Whenshown overlapping, it is meant to depict patterns that are suitable for acceptable communications given the purpose under prevailing conditions.
For simplicity, one-dimensional transmission patterns are shown and described herein. It is important to note, however, that the misalignment of beams and any adjustments made based thereon, as shown and described herein, may not only be in theazimuth (i.e. horizontal) or elevation (i.e. vertical) dimensions, but also a combination thereof. That is, misaligned beams as shown and described herein may be misaligned in the azimuth dimension, the elevation dimension, or a combination thereof. Similarly, adjustments made to correct misaligned beams according to the present invention may be performed in the azimuth dimension, the elevation dimension, or combination thereof. Further, beam width as used herein may be horizontal beam width orvertical beam width. That is, when adjusting beams by adjusting their beam width, the beam may be adjusting its horizontal beam width, vertical beam width, or a combination thereof.
For convenience, the present invention is described between a base station and WTRU, but may of course be implemented between WTRUs as desired. Once contact is established between a wireless communication system and a WTRU, they will negotiatethe use of beam forming. Both entities will agree to beam form only when the WTRU's rotation and location (both azimuth and elevation) are deemed sufficiently stable. This could be, for example, a setting in the WTRU established by interaction with theuser, motion sensors in the WTRU, or monitoring of the characteristics of the communication channel. The actual degree of beam forming from each entity is a function of power available, distance, and mitigating factors beyond the control of thetransceivers (e.g. fading, multipath, environmental conditions) and is preferably optimized with respect to power consumption and interference from and to other transceivers.
The table in FIG. 7 provides an example of four scenarios for both the up and down links with respect to the use of beam forming. The scenario that is used in each direction is a function of application need, the device's capabilities, the RFenvironment, and the physical stability of each device. In some circumstances the usage may be different in a given direction. For example, high speed targeted download may best be served by a tight downlink beam at both the sender and receiver(scenarios 72, 74) whereas an uplink acknowledge channel may be better served by an omni-directional transmission and beam formed receiver (scenario 76) to guarantee quick and reliable detection of ack or nack control signals.
In a first embodiment, wireless communication systems and the WTRUs operating therein are not capable of communicating and negotiating control of their respective use of beam forming. This may be a result of beam forming deployments in networksor devices which do not announce or negotiate their usage in a given area, for example. The usage of beam forming by both entities therefore becomes problematical as previously explained in connection with FIG. 6.
Therefore, in the first embodiment, control of beam forming in situations such as scenarios 72 and 74 is performed in a non-coordinated fashion to optimize the adjustment of misaligned beams and prevent the beams from falling into an oscillatingpattern, as explained in connection with the prior art. Referring now to the "before adjustment" portion of FIG. 8a, which is a plan view of two entities and their beams, at least one of two communicating entities 80, 82, say 80, will perform acorrection (i.e. an adjustment) that is equal to a fraction of the degree to which their respective beams 84, 86 are misaligned. That is, entity 80 will perform an adjustment that is a fraction of the error measurement. In this case, there will stillbe a degree of misalignment after the first few iterations of correction. For example, if one entity is attempting a full correction and the other is implementing the invention, any of the iterations prior to achieving the desired degree of alignmentwill result in an overshoot condition as shown in the "post adjustment" portion of FIG. 8a. Alternatively, if one entity is not adjusting its beam, or both entities are using the process of the present invention, and the adjustment fraction is less thanone-half of the error, the beams will undershoot on each adjustment. If the correction factor of the prior sentence is greater than one-half of the error, the beams will overshoot. Other combinations of percent of the correction factor and errors inmeasurement will cause under- or over-shoots. However, the degree of misalignment will decrease with each iteration in all cases wherein as long as one entity is implementing the present invention (i.e. performing an adjustment that is a fraction of theerror measured), convergence at a desired degree of alignment will occur. Once the desired degree of alignment is achieved, adjustments can cease until a degree of alignment less than the desired degree is again detected. Of course, the desired degreeof alignment may be set according to operator preference.
To further illustrate how beam alignment is achieved in the first embodiment, reference is now made to Table 1, shown below. In Table 1, three example scenarios are shown wherein the adjustment fraction (i.e. correction factor) that is used isone-half (0.5). The error measurements and adjustments are in degrees. In each scenario, entity "A" is using the invention and entity "B" is not.
TABLE-US-00001 TABLE 1 ERROR ENTITY A ENTITY B ITERATION MEASURED ADJUSTMENT ADJUSTMENT Scenario 1: Overlapping adjustment periods 0 32 16 32 1 16 8 16 2 8 4 8 3 4 2 4 4 2 1 2 5 1 0.5 1 6 0.5 0 0 Scenario 2: B adjusting before A 0 32 32 1 0 0 0Scenario 3: A adjusting before and more often than B 0 32 16 1 16 8 2 8 4 8 3 4 2 4 2 1 5 1 0.5 1 6 0.5 0
In the first scenario, entities A and B have overlapping adjustment periods. That is, they simultaneously (or nearly so) measure the degree of misalignment (i.e. the error) and adjust their respective beams so that they overlap in order tooptimize communications between them. However, as explained, they are not able to communicate regarding their respective use of beam forming. Therefore, to avoid falling into an oscillating pattern, entity A reduces its adjustment to 0.5 of the errorthat is measured. At iteration 0, an error measurement of 32 degrees results in entity A performing an adjustment of 16 degrees and entity B performing an adjustment of the full 32 degrees. These adjustments result in an error measurement of 16 degreesin iteration 1 (i.e. an overshoot condition as shown in the post adjustment scenario of FIG. 8a). Therefore, in iteration 1, entity A will again adjust its beam half of the error measured (i.e. 8 degrees) and entity B will again adjust its beam in anamount equal to the error measured (i.e. 16 degrees). The pattern continues until iteration 6 where 0.5 degrees is, in this scenario, the desired degree of alignment.
In the second scenario, entity B adjusts prior to entity A. At iteration zero, entity B measures an error of 32 degrees and adjusts its beam 32 degrees. Therefore, in iteration 1, when entity A performs its error measurement, it will not detectan error and will not make an adjustment.
In the third scenario, entity A is adjusting before and more often than entity B. During iterations 0 and 1, entity B takes no action and entity A simply performs its error measurements and adjusts its beam 0.5 of the error measured, as explainedabove. In iteration 2, there is an error measurement of 8 degrees. Entity A adjusts half of the error measured (i.e. 4 degrees) and entity B adjusts its beam in an amount equal to the error measured (i.e. 8 degrees). This pattern continues until adesired degree of alignment is obtained in iteration 6.
In FIG. 8a, the error measurements and adjustments are performed in the azimuth dimension. As shown in FIG. 8b, however, it is also possible to perform error measurements and adjustments in the elevation dimension. FIG. 8b is an elevation viewwherein a horizontal surface is shown in hash-marks. In FIG. 8b, the error measurements and adjustments that are made are the same as described in connection with FIG. 8a and Table 1, but they occur in the elevation dimension.
It is important to note that the error measurements and adjustments that are made to achieve a desired degree of alignment may need to be made in both the azimuth and elevation dimensions. To illustrate a scenario where adjustments are made inboth the azimuth and elevation dimensions, reference is now made to Table 2, shown below. The error measurements and adjustments are in degrees. In Table 2, as in the first scenario of Table 1, there are overlapping adjustment periods and entity A isusing the invention while entity B is not. In Table 2, however, there is misalignment in both the azimuth and elevation dimensions. Convergence to a desired degree of alignment in the azimuth and elevation dimensions is the same as explained abovewherein entity A performs azimuth and elevation adjustments that are a fraction (in this case 0.5) of their respective error measurements.
In iteration 1, an azimuth error of 32 degrees is measured and an elevation error of 40 degrees is measured. Therefore, assuming a correction factor of 0.5 for both dimensions, entity A adjusts its beam in the azimuth direction 16 degrees andentity B adjusts its beam in the azimuth direction the full 32 degrees. Similarly, entities A and B also adjust their respective beams in the elevation dimension 20 degrees and 40 degrees, respectively. As shown in Table 2, this pattern continues forentities A and B in both the azimuth and elevation dimensions until a desired degree of alignment is achieved in both dimensions (i.e. iteration 6).
TABLE-US-00002 TABLE 2 Overlapping Adjustment Periods (Azimuth and Elevation) AZIMUTH ENTITY A ENTITY B ELEVATION ENTITY A ENTITY B ERROR AZIMUTH AZIMUTH ERROR ELEVATION ELEVATION ITERATION MEASURED ADJUSTMENT ADJUSTMENT MEASURED ADJUSTMENTADJUSTMENT 0 32 16 32 40 20 40 1 16 8 16 20 10 20 2 8 4 8 10 5 10 3 4 2 4 5 2.5 5 4 2 1 2 2.5 1.75 2.5 5 1 0.5 1 1.75 .875 1.75 6 0.5 0 0 .875 0 0
Although in Table 2 the same correction factor (i.e. 0.5) is used in both dimensions, it is important to note that different correction factors may be used in the azimuth and elevation dimensions. Furthermore, although convergence is shown forsimplicity in Table 2 as being achieved in both dimensions at the same iteration (i.e. iteration 6), convergence in the azimuth and elevation dimensions may be achieved in different iterations.
Although the examples provided above are directed to specific scenarios for purposes of explaining the invention, there are of course an unlimited number of scenarios where error measurements are or are not being performed between two entitiesincapable of communicating control information regarding their respective use of beam forming. Regardless of the scenario, however, beams will converge (i.e. obtain a desired degree of alignment) as long as one entity is reducing its adjustmentaccording to the present invention.
In the above description of the first embodiment, the entity implementing the present invention utilized a correction factor of 0.5. That is, in the above description, the entity using the invention reduced its adjustment to 0.5 of whatevererror was measured. While a correction factor of 0.5 is preferred, the amount which the entity using the invention reduces the error measurement may be any number between 0 and 1.
In a second embodiment, a wireless communication system and WTRU are capable of communicating and negotiating control of their respective use of beam forming. In this embodiment, two entities may simply agree on an appropriate correction factor. For example, in the second embodiment, entity A and B may agree, for whatever reason, that entity A will perform an adjustment that is equal to 0.2 of the error measured and entity B will perform an adjustment that is equal to 0.8 of the error measured. Therefore, as shown in Table 3 below, in iteration 0 where an error of 32 degrees is measured, entity A performs an adjustment of 6.4 degrees and entity B performs an adjustment of 25.6 degrees. Then, in iteration 1, an error of 0 is measured and nofurther action is required. This situation is illustrated in the azimuth dimension in FIG. 9a and in the elevation dimension in FIG. 9b. FIG. 9a is a plan view and FIG. 9b is an elevation view wherein a horizontal surface is shown in hash-marks.
TABLE-US-00003 TABLE 3 Overlapping Adjustment Periods ERROR ENTITY A ENTITY B ITERATION MEASURED ADJUSTMENT ADJUSTMENT 0 32 6.4 25.6 1 0 0 0
In this embodiment, because two entities can negotiate their respective use of beam forming, the particular correction factor that is used by each entity may take into account factors affecting their communication. For example, the correctionmay be adjusted according to the capabilities of the entity, the angle between two communicating entities, and the power with which the entities are transmitting their respective beams.
With respect to the capabilities of the entities, base stations typically have better phase array antennas then WTRUs thereby allowing them to make finer adjustments to their beams. Where this is in fact the case, it may be desirable to have thebase station perform a larger portion of the adjustment by having the base station use a larger correction factor than the WTRU with which it is communicating.
With respect to the angle between two communicating entities, where there is a greater angle of adjustment needed for one entity than another, the entity with the greater angle of adjustment may use a greater correction factor. For example, fora WTRU being used in a car traveling past a base station with which it is communicating, the WTRU may need to adjust its antenna approximately 5 or 6 degrees for a correction whereas the base station, because it is using a wider beam, may only need toadjust its beam 1 or 2 degrees. Therefore, in this case, the majority of the adjustment may be allocated to the WTRU by having the WTRU use a greater correction factor than the base station.
With respect to the power with which the entities are transmitting their respective beams, a greater correction factor may be allocated to the entity transmitting with the highest power. That is, assuming a base station is transmitting at ahigher power than a WTRU with which it is communicating, it may be desirable to have the majority of any necessary adjustment performed by the base station to avoid further attenuation of the WTRU's signal. In fact, unless another factor requiresotherwise, it may be desirable to simply instruct the WTRU to refrain from moving its beam at all and have the base station perform an adjustment equal to 100% of the error measured. In this case, the correction factor for the WTRU is 0.0 and thecorrection factor for the base station is 1.0.
The errors measured and the adjustments made pursuant to the present invention may be made taking into account the orientation (azimuth and/or elevation) of the entities performing the error measurements and/or adjustments. For example, if anantenna is oriented 45 degrees downward in the elevation dimension to focus its beam toward the ground, any measurements and/or adjustments in the elevation dimension will account for the orientation of the antenna. Furthermore, it should be noted thatthe while this invention utilizes the terms azimuth (i.e. horizontal) and elevation (i.e. vertical) to refer to specific orientations, the invention is equally applicable to rotations of the axis from these nominal orientations. For example, there areinstances where antennas are intentionally setup such that they are specifically utilized at an angle offset relative to the nominal vertical or horizon planes. Cross polarization implementations, for instance, are often set at a 45 degree angle. Likewise randomly deployed or mobile equipment may not have a known or fixed relationship to orientations normally associated with the terms used. Additionally, while degrees of freedom for the width adjustments and boresight may ideally be implemented90 degrees relative to each other, it is also possible to implement the invention with any degrees of controllable freedom which are other than 0 degrees relative to each other.
The beam adjustments that are made pursuant to the present invention may be made using any appropriate parameter for adjusting beams. That is, correction of misaligned beams may be performed by adjusting any parameter capable of adjusting thebeam(s) so that they properly overlap.
For example, beam adjustment is typically performed by adjusting the boresight of a beam, the power with which a beam is being transmitted or the gain with which the signal is being received, or the width of a beam. Of course, beams may beadjusted by adjusting all three of these parameters or a particular combination thereof.
The adjustment parameters may be performed in the azimuth dimension, elevation dimension, or a combination thereof. Performing an adjustment in one dimension may affect the beam in another dimension. For example, when adjusting a beam's width(and not adjusting power and boresight) to correct beams that are misaligned in the elevation dimension, an increase or decrease in the beam's width in the elevation dimension will cause an equal decrease or increase in the beam's width in the horizontalposition
The particular adjustment parameter or parameters that are used to adjust a beam or beams in order to correct misalignment may be chosen, as desired, according to operator preference. That is, one embodiment may be where boresight adjustment isthe primary parameter for correcting misaligned beams wherein power and beam width are used in a secondary role where they are used to enhance or otherwise assist any adjustments made by adjusting a beam's boresight. For example, in this embodiment,where a correction of say 7 degrees needs to be performed in say an azimuth dimension, it may be desirable to use boresight to adjust the beams 5 degrees and increase/decrease (depending on whether the beam needs to be made larger or smaller) the powerand/or increase/decrease the width for the remaining 2 degrees.
In another embodiment, all of the parameters may be primary options so that they are all equally available options for correcting beam misalignments. In this case, again using boresight, power, and beam width as the available parameters, when acorrection needs to be made, the most efficient parameter for performing the correction may be used. For example, in situations where there is not a fine resolution on boresight control (i.e. a particular antenna does not have a high resolution withrespect to boresight control), any necessary adjustments, or the majority thereof, may be made by adjusting a beam's power or width.
Referring now to FIG. 10, there is shown a wireless communication system 100 wherein beams may be adjusted to enhance wireless communications between wireless entities (e.g. base stations and WTRUs) operating within the system 100. The system100 includes a plurality of wireless entities 104, 106, 108, 110 and at least one radio network controller (RNC) 102. Of course, the system components may vary according to the type of system in which the invention is being implemented. In system 100,wireless entities 104 and 106 are base stations while wireless entities 108 and 110 are WTRUs. The entities are capable of communicating using beam formed transmission and reception patterns and include a processor (see 112a for WTRU 110 and 112b forbase station 104) for measuring an error in the alignment of their own beam and the beam of another entity with which they are communicating. When two entities (say 104 and 110) are communicating and an error in the alignment of their respective beamsis detected, at least one of them will adjust their beam a fraction of the measured error as explained above. Additional processor(s) 114a, 114b may be provided for computing the fraction and adjusting the beam in an amount equal to the fractionmultiplied by the measured error. Otherwise, a single processor may be used for all of the functions performed pursuant to the present invention. Where two communicating entities are not negotiating or otherwise coordinating their respective use ofbeam forming, the computed fraction is preferably 0.5, as explained above.
In a preferred embodiment, the wireless entities may negotiate their respective use of beam forming and therefore communicate so that, for example, the fractions used by each entity to adjust their respective beams sum to one. While thedescription of this embodiment is in connection with WTRU 110, it is equally applicable to any wireless entity (e.g. any WTRU and any base station in system 100). As mentioned, WTRU 110 includes a processor 112a configured to measure an error in thealignment of a beam emanating from the WTRU 110 and another wireless entity, say base station 104, with which WTRU 110 is communicating. WTRU 110 also includes a processor 114a configured to compute the fraction and adjust its beam in an amount equal tothe computed fraction multiplied by the measured error.
In this embodiment, because two communicating entities negotiate their respective use of beam forming, it is preferable for at least one entity to actually compute a fraction based on the conditions of the communication (i.e. based on thedistance and/or angle between the two entities or the capability of one entities' antenna versus another, for example) and for one entity to simply use a fraction equal to one minus the computed fraction. For example, assuming WTRU 110 is communicatingwith base station 104, WTRU 110 will compute a fraction based on the conditions of the communication and communicate that fraction to base station 104. Base station 104 will then simply compute a fraction by subtracting 1 minus the fraction provided byWTRU 110. This enables each entities' 110, 104 respective beam to converge as explained in connection with FIGS. 9a and 9b.
To perform the negotiation of beam forming between wireless entities, the entities preferably include a transmitter and receiver for communicating control information regarding the use of beam forming. That is, continuing with WTRU 110 as anexample, WTRU 110 preferably includes a transmitter 116 configured to transmit any type of control information including the fraction with which WTRU 110 will adjust its beam to the entity with which WTRU 110 is communicating. The WTRU 110 alsopreferably includes a receiver 118 configured to receive any type of control information from another wireless entity with which WTRU 110 is communicating. The control information may include the fraction being used by the entity with which WTRU 110 iscommunicating. Of course whether WTRU 110 is receiving or transmitting a fraction may depend on whether WTRU 110 is the entity computing the fraction based on the conditions surrounding the communication, as opposed to using one minus whatever fractionthe other entity is using.
As mentioned above, the present invention is described in the context of infrastructure and mobile (i.e. WTRU and base station) communications. However, the use of beam forming between WTRUs is a natural extension of the present invention and iscertainly within the scope thereof. For example, if one of two communicating WTRUs can be established to be statically positioned, then the present invention may be implemented as outlined above. If two WTRUs are in relative motion with respect to eachother, then beam forming usage and correction of misaligned beams is also the same as above, but subject to the relative motion of the WTRUs. Further, in this embodiment, as with the embodiments described above, the errors that are measured and theadjustments that are made may be performed in the azimuth dimension, the elevation dimension, or both.
It is important to note that the present invention may be implemented in any type of wireless communication system, as desired. By way of example, the present invention may be implemented in UMTS-FDD, UMTS-TDD, TDSCDMA, CDMA2000 (EV-DO andEV-DV), any type of wireless local area network (WLAN), or any other type of wireless communication system. Further, while the present invention has been described in terms of various embodiments, other variations, which are within the scope of theinvention as outlined in the claim below will be apparent to those skilled in the art.
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